A conventional print head of a dot printer is shown in Japanese Laid-Open Patent Application No. Sho 57-163579 dated Oct. 7, 1982.
This print head consists of a plurality of electromagnets supported on a reel which has a core and at least one winding having an electrical connecting pin, a printed circuit board fixed to the electromagnets by soldering, a connecting means for connecting the circuit board to an outside electrical-circuit, and an insulating plastic means for covering said electromagnets and printed circuit board other than at the connecting means.
This print head has a flat lug projecting outwardly from the printed circuit board, which is ring shaped and the connecting means is a connector fixed on said flat lug.
If a large force is applied to the printed circuit board when a cable is detached from or attached to the connector, wiring on the printed circuit board and the connecting pins may be broken from the base at the soldered junctions therebetween.
As force applied to the connector at the time of connecting or disconnecting the connector has to be received by the printed circuit board, the board must have a sufficient thickness for obtaining the necessary strength,
If the connector is given a shock by falling during transport or assembling, it may be broken and the soldered portion may be displaced.
Another conventional print head is shown in Japanese Laid-Open Utility Model Application No. Sho 58-94529 dated June 27, 1983.
This print head consists of a plurality of needles, a nose for supporting a guide member for guiding said needles, and a plurality of iron core frames, on which needle driving coils are arranged circumferentially, and said iron core frames are each connected to the nose by means of a heat transmitting member.
This print head has a heat radiation member having many fins, and the iron core frame is fitted on the inside of the heat radiation member. The heat generated during the operation of the print head is conducted to the heat radiation member through a connection between the heat radiation member and the iron core frame. The heat is conducted from a cylindrical inner wall spaced from the bottom of the iron core frame mounted on the core which is a heat conducting path from the solenoid, which is a heat generator, to the inner wall of the heat radiation member. The connecting area between the heat radiation member and iron core frame is determined by the connecting pressure.
Therefore, the heat conducting efficiency is poor thus, this print head is conducts in that the generated heat the outside poorly.
Another conventional print head for a printer is shown in Japanese Laid-Open Utility Model Application No. Sho 60-38757, dated Mar. 18, 1985. This print head has more than one circuit pattern. One of said circuit patterns is a grounding circuit. The grounding circuit has a conductive material leaf on one end thereof for collecting static electricity. The conductive material leaf of the flexible printed circuit is contacted with a back surface of the print head, but the contacting pressure is insufficient and unstable. Therefore, static electricity generated on the paper being printed collects on the print head. This static electricity causes wrong motions of the needles.
Another conventional print head for a printer is shown in Japanese Laid-Open Utility Model Application No. Sho 63-21035 dated Feb. 12, 1988. This print head has a thermal sensing mechanism. The mechanism as described has thermal sensing elements mounted on the outer periphery of the solenoid base. Terminals of the thermal sensing elements are fixed to the base.
This conventional print head has defects as follows:
Firstly, the temperature difference between the solenoid and each thermal sensing element is great. Heat from the solenoid is conducted to the outer periphery, of the base from the core through the bottom surface of the solenoid base. The temperature difference between the solenoid and thermal sensing element may become great.
If the mechanism for mounting the thermal sensing element does not have a heat sink for cooling the print head, the sensing element is cooled by being exposed to the air directly. Therefore, the proper temperature of the solenoid cannot be detected.